

A261617


Numbers n such that n!!! + 3^n is prime.


0



0, 2, 16, 17, 20, 22, 28, 31, 37, 40, 53, 65, 71, 73, 82, 124, 130, 187, 203, 266, 308, 326, 386, 502, 662, 1919, 3136, 3229, 4640, 8113, 8659, 12307, 20972, 26408, 49391
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

n!!! is the triple factorial sometimes written n!3.
a(36) > 50000.


LINKS



EXAMPLE

2 is in the sequence because 2!!!+3^2 = 2+9 = 11 is prime.


MATHEMATICA

MultiFactorial[n_, k_] := If[n < 1, 1, If[n < k + 1, n, n*MultiFactorial[n  k, k]]];
Select[Range[0, 50000], PrimeQ[MultiFactorial[#, 3] + 3^#] &]


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



